Just one thing to note, you can't print white, so to get white emblems, this leaves you with a few options.
Print the emblem on white paper, trim close, and let set well. Then go back over the white overlap outside the emblem with the base coat paint.
Print the emblem on clear paper, leaving the white area open. Place the decal on the ship with white paint on the hull underneath. Then, go over the white overlap area with more base color, and let the white show through.
It is very, very tough to print a black outline on white paper and be able to trim it close enough to be convincing without leaving too much white or making the black outlines look wobbly. Trim close, and then line it with base color.
Whatever you do, if you're using decals, use something like Micro Sol/Set solution for best adhesion and shrinkage to the mini. Then, seal well. Testors Dullcoat lacquor works well, looks great, and is super tough. Use 2 coats.
As noted above, Microsoft Paint is plenty good for most things. One word of caution: Try a sample decal on a test mini first. NOT ALL PRINTER INKS ARE COMPATIBLE WITH DECAL PAPER. NOT ALL PRINTER INKS ARE COMPATIBLE WITH DULLCOAT LACQUOR.
Ask me how I know?!!! One ruined ace perfectly painted text book Hyperion later (with nasty ruined wrinkly decal plastic and runny ink), I just bought the decals from Griffon Games. They're crisp, clear, and work great.
Tom